Antibacterial textile finishes utilizing zinc acetate and hydrogen peroxide

ABSTRACT

The preparation of bacteriostatic, water-insoluble peroxide-containing complexes of zinc acetate, by reaction of zinc acetate with hydrogen peroxide in the presence of acetic acid, is disclosed. A process for in situ formation and deposition of these complexes on cellulosic and polyester textiles is described. The textile finishes so produced inhibit the growth and spreading of odor- and infection-producing gram-positive and gram-negative bacteria on the treated textiles. The antibacterial activity of the finished textiles is durable to repeated launderings.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates to a new method of imparting antibacterialactivity of textiles made of cellulosic fibers, polyester fibers orblends of cellulose with polyester.

(2) Description of the Prior Art

Although many types of antibacterial agents have previously been appliedto cellulosic and non-cellulosic textiles, the resulting textilematerials have generally been deficient in certain properties essentialto successful commercial use. Seldom have the products possessed acombination of strong activity against undesirable species of bacteria,together with the necessary durability to repeated laundering. In manyinstances, previous antibacterial agents have produced undesiredphysiological side effects on contact with human skin or exposed tissue,or they adversely affected the color, suppleness, softness, andabsorbency of the textile. In addition, such agents have usually beenexpensive to manufacture. Various types of antibacterials previouslystudied for textile applications have been described by Gagliardi,American Dyestuff Reporter 51 [2] P49-P58 (1962).

It has been known for many years that hydrogen peroxide is a safe andeffective topical and oral antiseptic and disinfectant when used indilute aqueous solution, and it can be used to cleanse open wounds. Byitself, it has no substantivity for cellulosic or polyester materials,and is removed in a single washing from yarns or fabrics to which it isapplied.

Recently, however, hydrogen peroxide has been shown to form colorless,water-insoluble complexes with zirconyl acetate, and these complexes canbe formed in situ as durable deposits on cellulosic textiles, therebyimparting considerable antibacterial activity (Vigo et al, TextileChemist and Colorist 9 [4] 77-80 (1977); Welch et al, co-pending U.S.Patent Application, Ser. No. 787,177 filed Apr. 12, 1977). Theantibacterial activity of the treated textiles appears to be due to aslow, controlled release of hydrogen peroxide as the effectiveantibacterial agent. This peroxide release as the textile surfaceappears to result from the slow reaction of zirconyl acetate-hydrogenperoxide complexes with the region moisture present in cellulosic fibersof the textile at equilibrium with air at ordinary humidity. In order toobtain even a peroxide content of 0.30%-0.35% in treated fabric, a veryhigh concentration of zirconyl acetate had to be applied, and this ledto fabric weight gains of 12%-16%. Such high fabric loadings increasedthe stiffness, caused a somewhat harsh feel, and decreased thewettability and absorbency of the fabric to an undesirable extent.

It is also well known that a simple, insoluble peroxide of zinc havingthe formula ZnO₂ can be prepared by adding solid zinc oxide to asolution of hydrogen peroxide containing small concentrations of mineralacid. The product forms as a granular solid (Wood and Clennett, U.S.Pat. No. 2,563,442). A similar product has been made by treating thebasic carbonate of zinc in solid form with concentrated hydrogenperoxide (Laporte Chemicals Ltd., French Pat. No. 1,524,638).

SUMMARY OF THE INVENTION

A process for imparting antibacterial activity to cellulosic andpolyester textiles is disclosed wherein the textile is treated with anaqueous solution which contains 1%-30% by weight of zinc acetate and1%-30% of hydrogen peroxide, and which, at zinc acetate concentrationsof 5% or greater, also contains 1%-25% of acetic acid, the textilesubsequently being heated to drive off water and acetic acid, therebyconverting the water-soluble reagents to insoluble peroxide complexes ofzinc acetate deposited on the textile.

The new treatment is applicable to unfinished textiles and also tocellulosic textiles having a durable press finish. The new treatmentinhibits the growth and spreading of odor- and infection-producingbacteria on the textile, and the antibacterial activity imparted isdurable to repeated laundering.

The present invention also includes the preparation of thewater-insoluble peroxide complexes of zinc acetate in the absence of acellulosic or polyester substrate, as a means of obtaining antibacterialdusting powders.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The processes of the present invention are based on the discovery thatzinc acetate forms hitherto unknown water-insoluble complexes uponreaction with hydrogen peroxide. These complexes are more stable andcontain a much higher percentage of bound peroxide, than is the case forzirconyl acetate-hydrogen peroxide complexes of the prior art. Also, theantibacterial activity of the peroxide available in the zinc complexesappears to be considerably augmented by the presence of the zinc ions,which in themselves are known to possess considerable antibacterialactivity (Rowland et al, American Dyestuff Reporter 65 [7] (1976);Gagliardi, loc. cit). The complexes are also more active on polyestertextiles than is the case with the zirconyl complexes.

However, no method is known for impregnation of textiles with thisinsoluble compound to give a uniform, durable, non-dusting film aroundthe fibers of the textiles. The zinc acetate-hydrogen peroxide reactionproducts of the present invention contain a significant proportion ofacetyl groups as indicated by chemical analysis, and differ in thisrespect from the simple zinc peroxide known to the prior art. Moreover,the prior art offers no means of preparing a homogeneous solution whichcan be applied to textile materials, and from which insoluble complexescontaining both zinc and peroxide can subsequently be deposited on thesurface of a textile.

In the processes of this invention, the zinc acetate used may be eitherthe anhydrous salt or the more widely available dihydrate having theformula Zn(OOCCH₃)₂.2H₂ O, but in the description that follows, allpercentages are by weight and refer to the anhydrous compound, exceptwhere specifically stated otherwise.

The processes of this invention are based on the discovery that zincacetate reacts with hydrogen peroxide in aqueous media to form solid,colorless, water-insoluble complexes whose elemental analyses correspondto the structure

    CH.sub.3 COO(ZnO-O).sub.x (ZnO).sub.y ZnOOCCH.sub.3

where x has values in the range of 9-16, and y has values in the rangeof 1-7. The value of x and y vary with the proportions of zinc acetateand hydrogen peroxide used in carrying out the reaction. The analysesindicate that these water-insoluble products are polymeric complexesderived from three simple compounds; namely, zinc peroxide, zinc oxideand zinc acetate.

The reaction to form these complexes proceeds to completion only if thewater present as solvent, and the acetic acid formed as co-product, areremoved by evaporation. The evaporation can be hastened by heating themixture at atmospheric pressure or under partial vacuum, the pressurebeing in the range of 0.1-1 atmosphere.

Since hydrogen peroxide is much less expensive mole for mole than zincacetate, it is preferable to carry out the reaction in the presence ofexcess hydrogen peroxide, especially since some hydrogen peroxide may belost through volatilization during the evaporation step. At zinc acetateconcentrations of less than 5% (or less than 6% calculated as as zincacetate dihydrate) the mixing of zinc acetate, hydrogen peroxide andwater yields slightly hazy but still reasonably uniform and usablesolutions. At higher concentrations of zinc acetate, however,precipitates of peroxide complexes appear. This precipitation can beprevented and even reversed by the addition of 0.2-3.0 parts by weightof acetic acid per part of zinc acetate, to give an acetic acidconcentration of 1%-25%. The addition of acetic acid is essential whenit is desired to apply the peroxide complexes as a concentrated uniform,homogeneous solution to textile materials and can also be advantageousin preparing batches of the solid complexes themselves, since anon-uniform product results when the composition of the initiallyprecipitated solids differs from that of solids subsequently formed asevaporation proceeds. The use of acetic acid for this purpose has theadvantage that this acid is volatile and readily removed by vaporizationalong with the water present. Evaporation to dryness converts thewater-soluble reagents to the desired water-insoluble peroxidecomplexes.

In preparing the solid, water-insoluble peroxide complexes, any order ofaddition and mixing of zinc acetate, hydrogen peroxide, acetic acid andwater is operable, but for preparation of a solution for application totextiles, it is somewhat preferable to mix zinc acetate with an excessof 25%-50% aqueous hydrogen peroxide, subsequently adding glacial aceticacid and finally adding water to obtain a homogeneous solution. Thisorder of addition resulted in somewhat greater retention ofantibacterial activity of the treated textile after repeated laundering.

Batches of the water-insoluble peroxide complexes of zinc acetate may beprepared using a wide range of reagent proportions and concentrations,the only limitations being the solubility limit for zinc acetate or itsdihydrate, and practical considerations of economy, which make itpreferable to use more than one mole of hydrogen peroxide per mole ofzinc acetate. The aqueous reaction mixtures may contain 1%-30% zincacetate, and preferably from 1.5 to 10.0 moles hydrogen peroxide permole of zinc acetate or its dihydrate, to give a hydrogen peroxideconcentration of 1%-50% in the mixture. Addition of 1%-25% acetic acidis carried out to give a clear solution. One evaporation of the mixture,a colloidal suspension is often produced which is difficult to filter.Therefore the mixture is preferably evaporated to complete dryness tocoagulate the colloidal particles. The solid residue is then washed withwater to remove any soluble impurities or unreacted starting materials,and the water-insoluble peroxide complexes are isolated by filtrationand drying. The temperatures used in the evaporation and drying stepsare preferably in the range of 50°-120° C. to avoid possibledecomposition and loss of peroxide complexes that might take place athigher temperatures, although these complexes are fairly stable totemperatures as high as 160° C. for short intervals, not exceeding 5minutes.

The above findings have been used to develop the process of the presentinvention for the preparation of bacteriostatic textiles. This processcomprises the following steps:

(a) immersion of a cellulosic or polyester textile in an aqueoustreating solution which contains about from 1% to 30% zinc acetate andfrom 1% to 30% hydrogen peroxide in water, and which, at zinc acetateconcentrations of 5% or greater, also contains from 1% to 25% aceticacid to prevent precipitation of peroxide complexes of zinc acetate, (b)removal of excess treating solution from the textile, (c) heating thetextile at a temperature of from about 50° C. to 160° C. for from 0.5minutes to 30 minutes in order to dry the textile and cause depositionof peroxide complexes of zinc acetate on the textile, the highertemperatures being used for the shorter times, (d) washing the textilewith water to remove excess reagents, and (e) drying the treated textileat a temperature of 50° C. to 140° C. for from 0.5 minutes to 30minutes.

In step (a) the above textile finishing process, the preferred moleratios of hydrogen peroxide to zinc acetate are 1.5-10.0 as alreadyindicated for the preparation of the peroxide complexes themselves, butmole ratios outside this range are also operative. The maximumconcentration of zinc acetate that can be used is fixed by thesolubility of this compound in water at room temperature. The use ofhydrogen peroxide at greater than a 30% concentration leads to excessdegradation and strength loss in cellulosic textiles. The presence ofacetic acid in the treating solution is essential for bath homogeneitywhen the zinc acetate concentration equals or exceeds 5%, as alreadyindicated. The preferred weight ratios of acetic acid to zinc acetateare in the range of 0.2-3.0 for the textile treatment as well as for thepreparation of the complexes, but other ratios are operative. Thepreferred order of addition in preparing the treating solution is thatof adding the acetic acid to a mixture of zinc acetate and 25%-50%aqueous hydrogen peroxide, and finally adding the water. However, thisorder is optional and examples of the inverse order of addition areincluded below. In carrying out step (a), the textile used may beroving, yarn or fabric regardless of whether spun, knit, or woven, ormay be nonwoven sheets or webs. The textile may be made of cellulosicfibers, polyester fibers or blends of these.

Yarns and fabrics already finished with a durable press reagent such asdimethyloldihydroxyethyleneurea or dimethylolethyleneurea are likewisesuitable for this process. In wetting the textile in the treating bath,ordinary textile equipment and methods suitable for batchwise orcontinuous passage or roving, yarns or fabrics through an aqueoussolution may be used, at any speed permitting thorough and uniformwetting of the textile material. If a wetting agent is used to increasethe rate and completeness of wetting, such an agent should be nonionicin order that the precipitation of zinc complexes in the treating bathmay be avoided.

In step (b) the excess textile treating solution may be removed byordinary mechanical methods such as by passing the textile betweensqueeze rolls, by centrifugation, or by draining.

In step (c), the purpose of heating the impregnated textile is to driveoff water and acetic acid by volatilization, and to convert thewater-soluble zinc acetate and hydrogen peroxide to water-insolubleperoxide complexes of zinc acetate deposited in the textile material ina form durable to removal by subsequent laundering. The peroxidecomplexes are stable to temperatures of 50° C.-120° C. for long periodsof time, but at temperatures of 140°-160° C., the heating time shouldnot exceed 5 minutes, and much shorter times often suffice. The heatingmay be carried out in an oven, preferably one having a forced draft ofair directed at the surface of the textile and exhausting through a ventto remove fumes of acetic acid and water vapor.

Washing of the treated textile, step (d), may be done with either hot orcold water. The peroxide complexes of zinc acetate are stable,insoluble, and durable to the mechanical agitation, spraying and rubbingthat occurs in washing machines or in large scale continuous orbatchwise textile washing equipment.

Final drying, step (e), can be carried out by any ordinary means such asoven drying, line drying, or tumble drying in a mechanical clothesdryer. High temperatures, in excess of 140° C. for long periods, shouldbe avoided to ensure against thermal decomposition of the peroxidecomplexes in the textile finish. A drying temperature of 80°-120° C. for1-5 minutes is particularly preferred.

In the following examples, all parts and percentages are by weight.Analyses for zinc were run by X-ray fluorescence. Analyses for peroxide(--O--O--) content in treated fabric were conducted iodometrically by aprocedure similar to that of Wentz and Cates, Textile Research J. 45 691(1975), as follows: 50 ml deionized water, 1 ml of 37% aqueoushydrochloric acid and 1 ml of saturated aqueous potassium iodide wereadded to the weighed fabric sample in a flask, and the mixture washeated on a steam cone for 10 min. followed by titration withstandardized 0.1 N sodium thiosulfate. The peroxide content of isolatedzinc acetate-hydrogen peroxide complexes was similarly determined exceptthat sufficient hydrochloric acid was added prior to titration to bringall the complex into aqueous solution.

Antibacterial activity of treated fabrics was determined qualitativelyby the parallel streak test of the American Association of TextileChemists and Colorists (AATCC Test Method 147-1976) with thegram-positive bacteria Staphylococcus aureus. Quantitative tests forantibacterial activity were run by the Quinn method (AATCC Test Method100-1974; H. Quinn, Applied Microbiology 10 74-78 (1962)), usinggram-positive Staphylococcus epidermidis and gram-negative Klebsiellapneumoniae bacteria. Staphylococcus aureus and Klebsiella pneumoniaeproduce infections in skin wounds, sores, boils, lesions, and abscesses,while Staphylococcus epidermidis acts on human perspiration to causeundesirable odors often referred to as "body odor".

Antifungal activity of treated fabric was determined by adapting theQuinn procedure already mentioned to the use of Trichophytonmentagrophytes as inoculant. This fungus is one of the principal causesof ringworm infections of the feet (so-called "athletes' foot"), hands,nails, body, scalp, and bearded regions of the face (S. Shadomy, H. J.Shadomy and G. E. Wagner, Chapter 13 of "Antifungal Compounds. Vol. I.Discovery, Development and Uses", M. R. Siegel and H. D. Sisler,editors, Marcel Dekker, Inc., 1977, pp. 442-444). The reduction inamount of fungus found in a treated fabric, relative to untreatedcontrol fabric, was determined by microscopical observation andexpressed in graded terms: none, slight, moderate, substantial, andcomplete.

Wrinkle recovery of treated fabrics was measured by the recovery anglemethod of the American Association of Textile Chemists and Colorists(AATCC Test Method 66-1975). Durability of fabric finishes to launderingwas determined in an agitator-type washing machine and tumble dryer ofthe type specified in AATCC Test Method 124-1975, using normalconditions for cotton (14 min. hot water wash, 30 min. high temperaturedrying) with the commercial AATCC standard detergent 124. The 80×80desized, scoured, and bleached cotton printcloth used weighed 3.2 oz.per square yard. Polyester and blend fabrics were similar in havingprintcloth construction.

EXAMPLE 1 Preparation of Zinc Acetate-Hydrogen Peroxide Complexes

(A) To 40.0 parts by weight of zinc acetate dihydrate in a beaker wasadded with stirring 125 parts of 30% aqueous hydrogen peroxide, 34.6parts glacial acetic acid, and 52.8 parts of water. The resultingsolution was transferred to a round bottom flask which was then attachedto a rotary evaporator fitted with a water bath and connected to a wateraspirator. The solution was evaporated under reduced pressure for 4 hrs.at 70° C., and thereafter for 2 hrs. at 50° C. The gummy residue wascooled to 25° C., transferred to an evaporating dish and dried in anoven to 85° C. for 135 min. The light yellow solid was broken up,powdered and slurried with 200 parts water. The slurry was filtered bysuction, was washed four times with 25 parts water and was filteredafter each washing. The white solid was dried at 85° C. for 15 min. Bychemical analysis, it was found to contain 22.3% peroxide, 65.7% zinc,and 2.40% carbon. All the carbon was present as acetyl groups, asindicated by a measured acetyl content of 5.3%. The analyses correspondto a polymer of the formula

    CH.sub.3 COO--ZnO--O).sub.14 (ZnO).sub.5 ZnOOCCH.sub.3.

(b) the preparation of the complex was carried out by a proceduresimilar to (A) except that quantity of glacial acetic acid used inmaking up the initial zinc acetate dihydrate-hydrogen peroxide-aceticacid solution in water was only 21.0 parts by weight. The mixture wasmechanically shaken for 30 min in a stoppered flask, whereupon a clearsolution was obtained. The product was a white solid analyzing 22.5%peroxide, 65.5% zinc and 3.09% carbon. All the carbon was present asacetyl groups, as indicated by a measured acetyl content of 5.9%. Theanalyses correspond to a polymer of the formula

    CH.sub.3 COO--ZnO--O).sub.11 (ZnO).sub.2 ZnOOCCH.sub.3.

EXAMPLE 2 Application of Zinc Acetate-Hydrogen Peroxide Solution toCotton at High Acetic Acid Concentration

To 40.0 parts by weight of zinc acetate dihydrate in a beaker were addedwith stirring 125 parts of 30% hydrogen peroxide, 34.6 parts of glacialacetic acid and 52.8 parts of water, to give an aqueous solution similarin composition to the solution of Example 1-A, and containing 15.8% zincacetate dihydrate, 14.9% hydrogen peroxide and 13.7% acetic acid.Desized, scoured and bleached 80×80 cotton printcloth was immersed inthe solution until thoroughly wet, and was then passed between squeezerolls of a wringer, with the roll pressure adjusted to give a wet pickupof 108%. The fabric was heat-cured in a forced-draft oven for 5 min. at85° C. It was then washed for 15 min. in hot running water at 60° C.,and oven-dried for 5 min. at 85° C.

The fabric had a weight gain of 4.2%, and contained 0.74% boundperoxide, as well as 2.70% zinc. Samples of the treated fabric weregiven repeated launderings in an automatic clothes washer and a tumbledryer. The fabric samples were then analyzed for zinc and peroxidecontent, and tested by means of the AATCC parallel streak test forantibacterial activity using Staphylococcus aureus as the inoculant. Theresults of these tests are shown in Table I.

                  Table I                                                         ______________________________________                                               Number         %             Width of                                         of Laun- %     Per- Bacterial                                                                              Inhibition                                                                           Test                               Fabric derings  Zn    oxide                                                                              Undergrowth                                                                            Zone   Rating                             ______________________________________                                        treated                                                                              0        2.7   0.74 None     3.0 mm.sup.a                                                                         passed                                    5                   None     2.5    passed                                    20       0.6   0.23 None     0      passed                                    35                  None     0      passed                                    50       0.2   0.12 Very slight                                                                            0      passed                             untreated                                                                            0        0.0   0.02 Extensive                                                                              0      failed                             ______________________________________                                         .sup.a Average of duplicate experiments                                  

Samples of treated and laundered fabrics were also subjected to theQuinn test for antibacterial activity using Staphylococcus aureus,Staphylococcus epidermidis and Klebsiella pneumoniae as inoculants. Theinoculated fabrics were incubated, and bacterial colonies wereafterwards counted under a microscope. The percent decrease in colonycount relative to untreated, unlaundered fabric was calculated. Theresults are shown in Table II.

                  Table II                                                        ______________________________________                                        Number of Percent Decrease in Colony Count                                    Launderings                                                                             S. aureus  S. epidermidis                                                                            K. pneumoniae                                ______________________________________                                         0        100        100         100                                          10        100                    71                                           20                   100                                                      25        100                    16                                           50        100        100         12                                           ______________________________________                                    

The test results show that the application to cotton fabric of the abovezinc acetate-hydrogen peroxide-acetic acid formulation made the fabriccompletely resistant to the growth of these three species of bacteria onthe fabric surface. The treated fabric retained its activity against twospecies of bacteria even after 50 launderings and tumble-dryings.

Inoculation and incubation of treated fabrics with Trichophytonmentagrophytes, a fungus active in causing ringworm of the feet andhands, was carried out in a manner analogous to the Quinn test, above.Treated, unlaundered fabric showed substantially decreased fungal growthas compared to untreated fabric, and even after twenty launderingcycles, the treated fabric still showed moderately decreased fungalgrowth.

EXAMPLE 3 Effect of Curing Temperature Used in Fabric Treatment

Fabric treatment was carried out using the procedure and conditions ofExample 2, except for the temperature used in the heat-curing step. Theproperties of the treated fabrics are shown in Table III, in terms ofzinc and peroxide content, and activity against Staphylococcus aureus inthe parallel streak test.

                  Table III                                                       ______________________________________                                                 Fabric         %    Bacterial                                                                            Width of                                  Cure     Weight  %      Per- Under- Inhibition                                                                           Test                               Temperature                                                                            Gain    Zn     oxide                                                                              growth Zone   Rating.sup. c                      ______________________________________                                        23° C..sup.a                                                                    3.3%    1.68   0.48 None   2.0 mm passed                             85.sup.b 4.2     2.70   0.74 None   3.0    passed                             120      4.0     3.26   0.79 None   2.0    passed                             140      3.9     2.80   0.80 None   2.5    passed                             160      3.6     3.41   0.79 None   4.0    passed                             ______________________________________                                         .sup.a Cure time: 24 hrs in this run only, 5 min. in all other runs.          .sup.b Same duplicate runs as in Example 2, Table I.                          .sup.c For behavior of untreated fabric, see Table I.                    

The data show that a wide range of curing temperatures are suitable forthe process of binding zinc ions and peroxide to cotton to impartantibacterial activity to cotton fabric.

EXAMPLE 4 Application of Zinc Acetate-Hydrogen Peroxide Solution toCotton at Medium Acetic Acid Concentration

To 40.0 parts by weight of zinc acetate dihydrate in a flask were addedwith agitation 125 parts of 30% hydrogen peroxide, 21.0 parts of glacialacetic acid, and 52.8 parts water. The flask was then stoppered andmechanically shaken for 30 min. to give a clear solution like that ofExample 1-B. The solution was applied to 80×80 cotton printcloth usingthe procedure and conditions of Example 2. The gain in weight of thefabric was 6.5%. The treated fabric was analyzed for zinc and peroxidecontent. Subsequently samples of the treated fabric were repeatedlylaundered and tumble dried, and tested for activity againstStaphylococcus aureus by the parallel streak method. The results areshown in Table IV.

                  Table IV                                                        ______________________________________                                                                  Bacterial                                                                            Width of                                     Number of                                                                              %      %         Under- Inhibition                                                                           Test                                  Launderings                                                                            Zn     Peroxide  growth Zone.sup.a                                                                           Rating.sup. b                         ______________________________________                                         0        2.8   0.93      None   3.0 mm passed                                 5                        None   1.8    passed                                20                        None   0.3    passed                                35                        None   0      passed                                50       0.72   0.27      very   0      passed                                                          slight                                              ______________________________________                                         .sup.a Average of duplicate experiments.                                      .sup.b For behavior of untreated fabric, see Table I.                    

Comparison of Table IV with Table I shows that decreasing the aceticacid concentration in the treating formulation resulted in an increasein the peroxide content obtained in the treated fabric, both before andafter 50 launderings. Untreated fabric developed extensive undergrowthwhen inoculated with Staphylococcus aureus, and failed the parallelstreak test, whereas treated fabric showed no undergrowth and passed thetest even after many launderings.

Samples of fabric treated at medium acetic acid concentration weresubjected, after laundering, to the Quinn test for antibacterialactivity. Staphylococcus aureus, Staphylococcus epidermidis, andKlebsiella pneumoniae were used as inoculants. The decrease in colonycount relative to untreated unlaundered fabric was determined, as shownin Table V.

                  Table V                                                         ______________________________________                                        Number of  Percent Decrease in Colony Count                                   Launderings                                                                              S. aureus S. epidermidis                                                                           K. pneumoniae                                 ______________________________________                                         0         100       100        100                                           10         100                  62                                            20                   100                                                      25         100                   8                                            50         100       100         5                                            ______________________________________                                    

EXAMPLE 5 Effect of Order of Addition of Reagents in Preparing theFabric Treating Solution

To 52.8 parts by weight of water in a flask was added 125 parts of 30%hydrogen peroxide, 21.0 parts glacial acetic acid, and 40.0 parts zincacetate dihydrate. The flask was then stoppered and mechanically shakenfor 30 min. The resulting solution was applied to 80×80 cottonprintcloth using the procedure and conditions of Example 2. The treatedfabric was subjected to the parallel streak test for activity againstStaphylococcus aureus before and after repeated launderings. The resultsappear in Table VI.

                  Table VI                                                        ______________________________________                                                                          Width of                                    Number of                                                                              %      %        Bacterial                                                                              Inhibition                                                                           Test                                 Launderings                                                                            Zn     Peroxide Undergrowth                                                                            Zone   Rating.sup. a                        ______________________________________                                         0       3.07   1.04     None     2.0 mm passed                                5       2.39   0.90     None     0      passed                               20       1.20   0.56     Very slight                                                                            0      passed                               35       0.96   0.34     Very slight                                                                            0      passed                               50       0.77   0.20     Very slight                                                                            0      passed                               ______________________________________                                         .sup.a For behavior of untreated fabric, see Table I.                    

Untreated, unlaundered fabric showed extensive bacterial undergrowthafter inoculation with Staphylococcus aureus and failed the parallelstreak test. Treated fabric showed no bacterial undergrowth when testedbefore or after 5 launderings, and showed only slight undergrowth wheninoculated after 20-50 launderings. A comparison of Table VI with TabelIV indicates, however, that the fabric treatment of Example 4 was moreeffective after 5-35 launderings than was the treatment of the presentExample. The only difference in procedure was the order of addition ofreagents in making up the treating solution. The order of addition usedin Example IV is therefore preferred.

Samples of the treated fabric of the present example were also subjectedto the Quinn test using Staphylococcus epidermidis as the inoculant. Thetreated fabric showed a 100% decrease in bacterial colony count relativeto untreated, unlaundered fabric, and this decrease was maintainedthrough 0, 20, and 50 laundering cycles.

EXAMPLE 6 Application of Zinc Acetate-Hydrogen Peroxide Solution toCotton at Low Acetic Acid Concentration

To 52.8 parts by weight of water in a flask was added 125 parts of 30%aqueous hydrogen peroxide, 10.5 parts glacial acetic acid and 40.0 partszinc acetate dihydrate. The flask was then stoppered and mechanicallyshaken for 15 min. The resulting solution was applied to 80×80 cottonprintcloth using the procedure and conditions of Example 2. The fabricweight gain was 8.5%. Zinc and peroxide content, and antibacterialactivity against Staphylococcus aureus by the parallel streak test, areshown in Table VII.

                  Table VII                                                       ______________________________________                                                                          Width of                                    Number of                                                                              %      %        Bacterial                                                                              Inhibition                                                                           Test                                 Launderings                                                                            Zn     Peroxide Undergrowth                                                                            Zone   Rating.sup. a                        ______________________________________                                         0       3.38   1.22     None     8.0 mm passed                                5       2.46   0.80     None     1.0    passed                               20       1.10   0.50     None     0      passed                               35       0.72   0.35     None     0      passed                               50       0.65   0.23     None     0      passed                               ______________________________________                                         .sup.a For behavior of untreated fabric, see Table I.                    

Untreated, unlaundered fabric failed the parallel streak test withStaphylococcus aureus, showing extensive undergrowth after inoculationand incubation. Comparison of Table VII with Table I again shows thatdecreasing the acetic acid concentration in the treating formulationresults in an increase in the amount of peroxide bound to the fabric.The zinc content obtained also was increased.

Samples of the treated fabric were subjected to the Quinn test forantibacterial activity, using Staphylococcus epidermidis as theinoculant. Treated fabric gave a 100% decrease in bacterial colony countrelative to the count for untreated, unlaundered fabric, and thisdecrease was maintained through 20, 35 and 50 laundering cycles.

EXAMPLE 7 Effect of Varying Reagent Ratios in Preparing the FabricTreating Solution

A number of samples of 80×80 cotton printcloth were treated using theprocedure and conditions of Example 2 except that the relativeproportions of the zinc acetate, hydrogen peroxide an acetic acid in thetreating solution were varied. The properties of fabric samples sotreated are shown in Table VIII in terms of percent zinc and peroxidebound to the fabric, and antibacterial activity of the fabric towardStaphylococcus aureus in the parallel streak test.

                                      Table VIII                                  __________________________________________________________________________                  Fabric                                                          Treating Bath Weight                                                                            %   %   Bacterial                                                                            Inhibition                                                                         Test                                    Zn(OAc).sub.2.sup.a                                                                 H.sub.2 O.sub.2                                                                   HOAc                                                                              Gain                                                                              Zn Peroxide                                                                           Undergrowth                                                                          Zone Rating                                  __________________________________________________________________________    16.0%.sup.b                                                                         14.9%                                                                             13.2%                                                                             4.2%                                                                              2.70                                                                             0.74 None   3.0 mm                                                                             passed                                  16.0   7.5                                                                              13.2                                                                              3.3 0.81                                                                             0.34 None   3.0  passed                                  8.0   14.9                                                                              13.2                                                                              3.6 1.18                                                                             0.38 None   2.0  passed                                  8.0   17.3                                                                              13.2                                                                              3.1 1.39                                                                             0.44 None   2.0  passed                                  8.0   14.9                                                                              21.2                                                                              2.4 0.96                                                                             0.27 None   1.5  passed                                  5.0   3.0 1.0 0.9 0.23                                                                             0.07 None   0    passed                                  5.0   3.0 0   1.5 0.57                                                                             0.20 None   2.0  passed                                  5.0   0   0   0.8 0.20                                                                             0.02 Extensive                                                                            0    failed                                  0.sup.c                                                                             0   0   0   0.02                                                                             0    Extensive                                                                            0    failed                                  __________________________________________________________________________     .sup.a % Zinc acetate dihydrate.                                              .sup.b Same duplicate runs as in Example 2, Table I.                          .sup.c Untreated fabric.                                                 

In those runs in which hydrogen peroxide was present in molar excessover the zinc acetate in the treating bath, the amount of hydrogenperoxide bound to the fabric was approximately proportional to the zincacetate concentration used. This indicates the zinc acetate and hydrogenperoxide are bound together as a complex which is deposited on thecotton.

The data also show that when a zinc acetate dihydrate concentration aslow as 5% is used, no acetic acid is required in the treating bath tosolubilize the zinc acetate-hydrogen peroxide reaction product. Only afaint haziness was observed in this treating solution, whereas at zincacetate dihydrate concentrations of 6% or higher, cloudiness andprecipitation resulted if no acetic acid were added.

EXAMPLE 8 Post-Application of Zinc Acetate-Hydrogen Peroxide to DurablePress Cotton Fabric

Cotton 80×80 printcloth which had been desized, scoured and bleached wastreated with a standard durable press finishing agent,dimethyloldihydroxyethyleneurea (DMDHEU), in the following way: thefabric was immersed and thoroughly wet in an aqueous solution containing11.0% DMDHEU together with 0.5% zinc nitrate hexahydrate which serves asa Lewis acid catalyst. The fabric was passed through a wringer adjustedto a squeeze roll pressure giving a wet pickup of 98%. The cloth wasoven-dried at 85° C. for 5 min. and then oven-cured at 160° C. for 3min. to produce cellulose crosslinking. The fabric was washed and thenredried at 85° C. for 5 min. The fabric weight gain was 7.8%. Thewrinkle recovery angle after the fabric was conditioned at standardhumidity was 287° (sum of warp and fill values). Untreated fabric had awrinkle recovery angle of 196°.

To this wrinkle resistant, durable press fabric was applied a treatingsolution containing 40.0 parts by weight of zinc acetate dihydrate, 125parts of 30% aqueous hydrogen peroxide, the amount of glacial aceticacid specified in Table IX and 52.8 parts water. The fabric was immersedand thoroughly wet in the treating solution, and was passed through awringer having squeeze rolls adjusted to give a wet pickup of 105%-120%.The fabric was heat-cured in a forced-draft oven for 5 min. at 85° C.,was afterwards washed for 15 min. in hot running water at 60° C., andwas oven-dried for 5 min. at 85° C. The zinc and peroxide content, andfabric performance in the parallel streak test with Staphylococcusaureus, are shown in Table IX.

                                      Table IX                                    __________________________________________________________________________    Acetic Acid                                                                           Fabric            Width of                                             in     Weight                                                                            % %    Bacterial                                                                            Inhibition                                                                         Test                                           Treating Bath.sup.a                                                                   Gain.sup.b                                                                        Zn                                                                              Peroxide                                                                           Undergrowth                                                                          Zone Rating                                                                            WRA.sup.c                                  __________________________________________________________________________    34.6 parts                                                                            9.5 3.0                                                                             0.90 None   5.0 mm                                                                             passed                                                                            278°                                21.0    7.6 2.5                                                                             1.15 None   5.0  passed                                                                            277                                        10.5    9.4 2.5                                                                             1.24 None   3.0  passed                                                                            271                                        __________________________________________________________________________     .sup.a Treating solution prepared as described in Examples 2, 4, and 6        respectively.                                                                 .sup.b Gain in weight during zinc acetate-H.sub.2 O.sub.2 -HOAc               application.                                                                  .sup.c Wrinkle recovery angle (warp plus fill).                          

In the absence of the zinc acetate-hydrogen peroxide post-application,the DMDHEU-treated printcloth failed to give a zone of bacterialinhibition in the parallel streak test. The results show that theprocesses of the present invention can be applied as readily to durablepress cotton fabrics as to untreated cotton. Fabric given thepost-application also gave 100% reduction of the Staphylococcusepidermidis colony count as observed in the Quinn test.

EXAMPLE 9 Application of Zinc Acetate-Hydrogen Peroxide to Polyester andCotton-Polyester Blends

The procedure and conditions of Example 2 were used in treatingprintcloth woven of yarn containing polyester blended with cotton in theproportions specified in Table X. The treated fabrics were machinewashed and tumble dried, and after a specified number of such launderingcycles, were subjected to the Quinn test for antibacterial activity,using Staphylococcus epidermidis as the inoculant. The results appear inTable X.

                  Table X                                                         ______________________________________                                        %     %        Percent Decrease in Colony Count                               Cotton                                                                              Polyester                                                                              0 Cycles    20 Cycles 50 Cycles                                ______________________________________                                        100    0       100         100       100                                      65    35       100         99        39                                       50    50       100         65        40                                       35    65       100         15        22                                        0    100       98         77        69                                       ______________________________________                                    

The data show that the treatment was more effective and durable onall-cotton fabric than on all-polyester fabric, but that a considerableantibacterial activity was imparted to all the fabrics treated.

EXAMPLE 10 Application of Zinc Acetate-Hydrogen Peroxide to Paper

To 52.8 parts by weight of water in a flask was added 125 parts of 30%aqueous hydrogen peroxide, 10.5 parts glacial acetic acid and 40.0 partszinc acetate dihydrate. The flask was then stoppered and mechanicallyshaken for 15 min. to yield a clear solution. White typewriting paper,25% bond, was immersed and thoroughly wet in the solution, and was freedof excess liquid by being passed between squeeze rolls of a wringer. Thepaper was heat-cured in a forced-draft oven for 5 min. at 85° C. It wasthen rinsed for 5 min. in water, and dried at 85° C. for 5 min. Thetreated paper contained 0.15% peroxide by titration. In the parallelstreak test with Staphylococcus aureus, it produced a 0.5 mm zone ofbacterial inhibition, whereas untreated paper produced no zone ofinhibition.

We claim:
 1. A process for the preparation of water-insoluble peroxidecomplexes of zinc acetate, which process comprises:(a) mixing zincacetate, hydrogen peroxide, acetic acid an water to give a solutionwhich contains about from 1% to 30% zinc acetate, 1% to 50% hydrogenperoxide and which at zinc acetate concentrations of 5% or greater, alsocontains 1% to 25% acetic acid, there being about from 1.5 to 10.0 moleshydrogen peroxide per mole of zinc acetate present, and from 0.2 to 3.0parts by weight of acetic acid per part of zinc acetate, the amount ofacetic acid used being that needed to produce a clear solution, (b)evaporating the mixture to dryness to yield a solid residue containingthe peroxide complex, (c) washing the solid, water-insoluble peroxidecomplex with water to remove water-soluble impurities and unreactedstarting materials, (d) filtering the solid, water-insoluble peroxidecomplex, and (e) drying the water-insoluble solid peroxide complex. 2.As bacteriostatic complexes, the solid, water-insoluble peroxidecomplexes produced by the process of claim 1 and characterized by thepresence of zinc, acetyl groups and peroxide groups in the complexes.